The invention relates to an industrial robot of, for example the types described in the following ASEA pamphlets: CK 09-1101E, CK 09-1102E, CK 09-1103E, CK 09-1109E, A 09-1030E, A 09-1111E, A 09-1113E.
Such a robot has several movement axes, typically six axes. For a certain axis the mass moment of inertia, the effect of gravity and the effect on the axis of movements in other axes may vary within wide limits in dependence on the current positions of all the axes and on the mass of the load borne by the robot. When designing and trimming the position control system of each axis, the control parameters must be limited so as to obtain rapid and stable operation also in the operating case which is most unfavorable from the point of view of control. This means that acceleration and deceleration of the axis movement generally will be far below the optimum values. This, in turn, means that the time taken for a movement between two points will be unnecessarily long, and this applies particularly to movements over short distances. In many applications, for example spot welding and assembly, the work program of the robot consists of a large number of relatively short movements. The so-called cycle time, i.e. the time for carrying out the program, will, especially for these applications, be long, which is a serious drawback from the point of view of economy and production technique.